1. Field of the Invention
The present invention relates to a novel process for producing aromatic (poly)ether-ketones and-sulfones. As used herein, the term "(poly)ether" designates "ether" or "polyether". Further, the present invention relates to a novel crystalline, high melting point aromatic polyetherketones.
2. Discussion of Related Art
A typical prior method for producing an aromatic ether-ketone and -sulfone comprises reacting a halide represented by the formula --Y--Ar--X, wherein Y denotes a ketone group or a sulfone group; Ar denotes a phenylene group or a nuclear-substituted product thereof; and X denotes a halogen atom, the halogen atom being bonded at the ortho- or para-position relative to Y, with a phenol represented by the formula --Ar'--OH, wherein --Ar' denotes a phenylene group, in the presence of alkali, as expressed by the following equation. ##STR2##
By a similar method, an aromatic polyetherketone or -sulfone has been synthesized from an aromatic dihalide and a bisphenol.
However, the above-mentioned method which utilizes a nucleophilic reaction has the following disadvantages: it requires two types of raw materials (namely, an aromatic halide and a phenol); since the reaction is carried out at a high temperature in the presence of alkali, undesirable side reactions of a phenol are apt to take place; in the synthesis of polyether-ketone and -sulfone, a high molecular weight product cannot be obtained unless the molar ratio between an aromatic dihalide and a phenol is strictly adjusted; further, since a thermally unstable hydroxy phenyl group is contained in about half of the polymer terminals, a terminal group-stabilizing treatment is required. Moreover, although, in this nucleophilic polymerization, it is possible to produce a polymer having a repeating unit of the formulae (II) or (III) R1 ? ##STR3## as disclosed in Japanese Patent Application Kokoku (Post-Exam. Publn.) Nos. 22,938/82 and 32,642/85, in order to produce a polymer which has a higher ketone-group content, higher melting point and greater heat resistance, for example, a polymer having a repeating unit represented by formula (IV) ##STR4## it is necessary to use a bisphenol of low reactivity ##STR5## and hence would necessitate the use of severe reaction conditions. As a result, a branching and/or gellation of the polymer chain takes place in the prior method and hence the intended linear polymer cannot be produced [Japanese Patent Application Kokai (Laid-Open) No. 96,700/77]. Further, when it was intended to synthesize a polymer with a still higher ketone content having a repeating unit of formula (I) a bisphenol of a still lower reactivity ##STR6## had to be used and a high molecular weight polymer could not be obtained.
On the other hand, apart from the above-mentioned method utilizing a nucleophilic reaction, a so-called Friedel-Crafts reaction method is known [Japanese Patent Application Kokoku (Post-Exam. Publn.) No. 34,419/81] which comprises forming a ketone group and sulfone group by means of an electrophilic reaction to produce an aromatic (poly)ether-ketones and -sulfones.
Since the former method and the latter method differ fundamentally one from the other in their reaction mechanism, the properties of the resulting polymers also differ one from the other. For example, a polymer obtained by the latter Friedel-Crafts reaction having the repeating unit of formula (II), ##STR7## has a low crystallinity as compared with a polymer ##STR8## obtained by the former nucleophilic reaction, and as a consequence, has a disadvantage of having a low modulus at such high temperatures as 200.degree. to 350.degree. C. and of an extremely high heat shrinkage of stretched film. This is because, while para-linkages are exclusively formed in a nucleophilic reaction, ortho and meta- linkages are formed in addition to the para-linkage, resulting in abnormal linkages and/or branching taking place in the polymer chain. Polymers having such abnormal linkages are poor in mechanical properties and, to secure the desired properties, must have a particularly high molecular weight, which, however, inevitably causes lowering in moldability and crystallinity.
Using the Friedel-Crafts reaction, there has been prepared a polyetherketone of a higher melting point having the structural formula ##STR9## However, this polymer contains abnormal linkages, is thermally unstable and hence cannot undergo thermoplastic processing. Moreover, in the reaction, an unstable xantohydrol group is formed at the polymer terminal during polymerization. Accordingly, a special operation involving a reduction treatment of the xantohydrol group is necessary for stabilizing the polymer [Japan - US Polymer Symposium, 259 (1985)]. Further, since the polymer contains abnormal linkages, in spite of its ketone content, it still has a low melting point. Thus, a value as low as 385.degree. C. has been solely reported for the polymer having repeating unit (I) [Japan - US Polymer Symposium, 259 (1985)].
Moreover, although usually HF-BF.sub.3 is used as the polymerization catalyst and solvent in the Friedel-Crafts reaction, HF-BF.sub.3 is unsuitable for commercial production since it is a very poisonous and corrosive substance. On the other hand, when another commonly used catalyst, aluminum chloride, is used, it has the defect of being more apt to form abnormal linkages and branching in the polymer structure than the above-mentioned HF-BF.sub.3 system. Further, the resulting polymer is contaminated with aluminum chloride, which can only be difficultly removed, and hence is inevitably poor in thermal stability.
Thus, aromatic polyetherketones obtained by the Friedel-Crafts reaction are different in polymer structure from their equivalent which had been obtained by a nucleophilic polymerization and also are poorer in practical properties. Accordingly, they have not yet been produced commercially.
Referring further to the related art, it has been reported that an aliphatic carbonate is formed when an aliphatic halide and an alkali metal carbonate are reacted in the presence of a cyclic ether [K. Sogs, J. Polymer Sci., Lett., 15, 611 (1977)]. In Example 17 of Japanese Patent Application Kokai (Laid-Open) No. 129,294/78 invented by the named author, polycarbonate having a molecular weight of 8,000 has been obtained by reacting dichlorodiphenylsulfone with potassium carbonate in the presence of 18-crown-6-ether at 160.degree. C. for 48 hours.